<!DOCTYPE html>
<html>
<body>
<script>
  // Create a bunch of nested flex containers:
  var parentNode = document.body;
  var depth = 50;
  for (var i = 0; i < depth; i++) {
    var childNode = document.createElement("div");
    childNode.style.display = "flex";
    parentNode.appendChild(childNode);
    parentNode = childNode;
  }

  // Add some text in the innermost child:
  childNode.innerHTML = "Text";

  // Force reflow:
  var height = document.body.children[0].offsetHeight;
</script>
